In the conventional technique, a cooling device that supplies cold water is equipped with cooling means, such as a chiller, for obtaining cold water cooled to a desired temperature. Such cooling means is equipped with a compressor, a condenser, pressure-reducing means, and an evaporator, and is provided with a refrigeration cycle that makes a refrigerant circulate therethrough.
A low-pressure low-temperature refrigerant liquid and a cooling fluid containing water as its main component circulate through the evaporator in a heat exchangeable manner. That is, the refrigerant liquid evaporates by receiving heating energy (evaporation heat) from the cooling fluid, whereas the cooling fluid is cooled by surrendering heating energy. In a case where the cooling fluid is used in an air-conditioning apparatus, conditioned air and the cooling fluid exchange heat in an air-conditioned space so as to cool or heat the air-conditioned space.
In a proposed example of a refrigeration and air-conditioning apparatus that performs cooling operation with high efficiency, “a cooling unit includes a condenser that is disposed outdoors and performs cooling using outside air and evaporators provided at positions lower in level than that of the condenser. Moreover, the cooling unit is equipped with refrigeration cycles configured to be switchable between thermo-siphon refrigeration cycle operation and refrigerant compression forced circulation refrigeration cycle operation. In the cooling unit, the refrigeration cycles are arranged in a plurality of stages in parallel with the single condenser. The evaporators of the refrigeration cycles in the plurality of stages are configured such that the evaporating temperature of the evaporator in the first stage is set high, and the evaporating temperatures of the evaporators decrease in turn from the second stage. Cooling load pipes are connected in series with the evaporators in the refrigeration cycles, sequentially from the first stage” (see, for example, Patent Literature 1).